This research is aimed at delineating the chemistry and physiology of a new series of iodinated and brominated perfluorocarbon X-ray contrast media for intravascular diagnoses. The fluorocarbon part is a good solvent for oxygen and carbon dioxide, as demonstrated by liquid breathing and other observations, while the bromine and iodine make the compounds radiopaque. Iodoperfluorochemicals and bromoperfluorochemicals will be synthesized and tested in the form of emulsions as intravenous oxygen transport agents (artificial blood) and as roentgenographic diagnostic agents. Tissue and mixed venous oxygen tensions, along with blood carbon dioxide tension and pH, will be used as criteria of oxygen transport capabilities. Standard and new methods will be used to test to radiopacity. Blood volumes will be measured as one of the practical means of evaluating isotonicity. The chemical stability and metabolic fate of these substances will be investigated by chemical analysis of the blood and tissues of animals receiving these emulsions. Such isotonic oxygen carrying media could be used for prolonged in vivo perfusion of organs, or even for the whole body, for detailed X-ray analysis.